This invention relates to optoelectronics, and in particular to soldering a component to a substrate.
In the field of optoelectronics, it has become increasingly important when mounting a light emitting device such as a laser to a base member to precisely control the position of the laser in order to ensure maximum light coupling to an optical fiber. Such positioning, therefore, is a key factor in determining the performance of the transmitter and the system of which it is a part. Often, if a device varies by only 1 micron from its nominal position, the assembly may be rendered worthless.
Typically, a device such as a laser is attached to a block of material such as Ag, which block is then soldered to the base member, which is typically a header comprising a steel alloy such as Kovar. Since the solder tends to creep, and the block usually has a thermal coefficient of expansion different from the base, the position of the laser can vary over a significant range from a coupling standpoint, e.g., approximately 1 micron. Sometimes a stop is used to hold the block in place at one edge. If the block is also soldered to the stop, the laser position will change due to solder creep. If the block is not soldered to the stop, the final position is unpredictable because of small variations in the solder thickness at the base of the block.
It is, therefore, desirable to provide a method and structure which provides an accurate positioning of a component which is soldered to a substrate.
The invention in accordance with one aspect is an optical assembly which includes a base member, a block of material soldered to the base member, the block including a centerline extending between first and second surfaces, and an optical component mounted on a third surface of the block. A pair of stop members are provided on the base member and make contact with the block at a surface other than the third surface, preferably at approximately the centerline of the block.
In accordance with another aspect, the invention is a method of bonding an optical component to a base member which includes the steps of mounting the component to a surface of a block of material having a centerline between first and second opposing surfaces, providing a base member having a pair of stop elements on a major surface thereof, and soldering the block to the surface of the base member while the stops make physical contact with the block at a surface other than that to which the component is mounted, preferably at approximately the centerline of the block.